Fossils and DNA strongly suggest we shared a common ancestor with them, genetic clocks placing the split between us in the range of 550,000 to 765,000 years ago.

Our fascination stems from the fact they are our closest evolutionary cousins; we have hundreds of fossils from them, so have a pretty good idea what they looked like; and they were the first extinct human species we knew about, with Neanderthal bones found discovered in the first half of the 19th century.

Neanderthals have historically also represented the archetypical brutish caveman in popular culture.

Each year dozens of research articles are published examining almost every aspect of their biology and behaviour, as gleaned from the fossil and archaeological records they have left behind.

When and where did they live?

The Neanderthals occupied Europe for at least 200,000 years, but our knowledge of them further east is much sketchier.

We also know they lived in West Asia, with their skeletons found in several caves in Israel and Iraq dating between around 140,000 and 50,000 years ago.

They inhabited Southern Siberia as well, particularly the Altai Mountains, about 50,000 years ago, occupying the same cave as the mysterious 'Denisovans', a closely related but probably distinct species from them.

But, whether they were there at exactly the same time as the Denisovans is anyone's guess.

Given the extreme cold associated with the glacial (cold) phases of the Ice Age, their occupation of Siberia probably wasn't permanent either.

In Europe, for example, they are known to have retreated south during these extreme cold phases, so probably had limited tolerance of extreme conditions, despite their sophisticated culture.

Just when did they disappear?

A long and protracted debate has been held among archaeologists for decades about just when the Neanderthals went extinct.

This has mostly been because some archaeological sites have been disturbed since they formed, so the fossil and stone tools they contain are mixed up, representing materials of different ages.

The other major reason has been that we simply didn't have the technology to determine the age of their bones reliably, especially when they were thought to be around 30,000 or 40,000 years old.

Laboratory methods developed over the last decade have pushed our ability to clean-up bones and other materials for radiocarbon dating, and to obtain much more accurate ages.

This has been truly revolutionary in places like Europe where archaeologists have been debating for decades when Neanderthals disappeared, when modern humans like us entered the subcontinent, and whether the two events coincided.

In short, a coincidence in the timing of these events would be the sort of 'smoking gun' most archaeologists are looking for to explain Neanderthal extinction.

The youngest Neanderthal fossil is from Mezmaiskaya in the northern Caucasus, and with an age of around 39,000 years old, it marks the most widely accepted disappearance date for the species.

But, the species probably went extinct over the course of several thousand years, and in different parts of Europe at different times.

Written in stone

Archaeologists who specialise in the study of stone tools attribute particular types of tools, grouped into 'industries' or 'cultures', with particular species of hominin.

The Neanderthals in Europe made an industry known as the 'Mousterian', named after a rock shelter called Le Moustier in the Dordogne region of France, which contained Neanderthal fossils and cultural remains.

In contrast, the earliest modern humans in Europe made a tool industry called the Aurigancian, named after another archeological site in France called Aurinac.

So, stone tools are used as markers of prehistoric migration, economic behaviour and also mental capacities and intelligence between species.

Compared to the Mousterian, the Aurignacian is often seen as a cultural flowering associated with the hallmarks of the modern human mind in all its richness and imagination.

It includes elements like complex and carefully shaped bone including antler and ivory tools; skillfully shaped stone and ivory beads and other kinds of personal ornaments; highly varied and sophisticated forms of abstract and figurative art that portray fine details of human anatomy such as male and female sex organs; and elaborate cave paintings.

Now, this is not to say that the Neanderthals didn't possess a complex culture, for there is controversial evidence they may have made art or even wore jewellery, possibly even buried their dead in graves in caves and rock shelters.

But, most archaeologists have no difficulty distinguishing the Aurignacian from the Mousterian.

Yet, having said this, there's one catch: the proto-Aurignacian. A tool industry that appeared in Europe about 42,000 years ago and was subsequently replaced by the 'true' Aurignacian.

This industry has been controversial for decades owing to the lack of a clear association between these tools and the toolmakers, or their skeletal remains.

Who made the proto-Aurignacian?

A new study reported last week in the journal Science by Stefano Benazzi from the University of Bolognia and his team has shown that modern humans were in Western Europe by 41,000 years ago at two sites called Riparo Bombrini and Grotta di Fumane in Northern Italy.

This makes them examples of the earliest modern humans in Europe.

Yet, the mystery deepens, because Benazzi and his team have also managed to solve the long-standing issue of just who made the proto-Aurignacian.

This is the million-dollar question! Was it modern humans or Neanderthals, perhaps copying their new modern human neighbours?

Benazzi and his team worked out the identity of two 41,000-year-old teeth found alongside proto-Aurgnacian tools at these two sites studying anatomical features and DNA from one of them.

They turned out to be modern humans after all, confirming there were multiple routes into Europe — one in the south and one in the north — these different groups carrying with them the proto-Aurgnacian and Aurignacian, respectively.

Neanderthal disappearance: whodunit?

With new radiocarbon dates on bones from both late Neanderthals and the earliest European modern humans, and the identity of the makers of the proto-Aurignacian now known, it looks increasingly likely that our cousins went extinct with a very short timeframe of our arrival: within the narrow window of 39,000-41,000 years ago.

While we don't, and probably never will, have direct evidence of exactly what happened, this strongly implies a role for modern humans in their disappearance.

Darren Curnoe will discuss this topic in more detail with Dom Knight on 702 Sydney tomorrow evening.

About the author:Associate Professor Darren Curnoe is an evolutionary biologist at the University of New South Wales. He writes about all aspects of evolution on his blog Walking on two feet. His work with colleague Ji Xueping is featured in the documentary Enigma Man: A Stone Age History. He also appears regularly on ABC 702.